if you run a "farm" of resources that execute different schemas and executions based on the day or load you would definetly benefit from a know execution time.
I do think that it's in the BP standard template a option to use X number of items or X number of hours/minutes. The latter one is in my opinion the one that actually work in a real world scenario. ( For example you want to utilize your resource or target system license etc. ) If you set a fixed exectiontime, as an example 1:50h to a process then you could:
I see many developers choose number of items as the delimiter, but we frankly work by the clock not by the item....
PS Of course the timeblock could be of any size DS